13C- and 1H-NMR studies on digeneaside in the red alga Caloglossa leprieurii. A re-evaluation of its osmotic significance

Abstract

The main organic solutes potentially involved in the osmotic acclimation of the euryhaline red alga Caloglossa leprieurii (Ceramiales) were analysed and spectroscopically characterised using natural abundance 13 C and 1 H nuclear magnetic resonance (NMR) spectroscopy and gas-liquid chromatography/mass spectrometry (GLC/MS). In a marine and a freshwater isolate of C. leprieurii the polyhydric alcohol D-mannitol played an important role as osmolyte. The heteroside digeneaside (α-D-mannopyranosyl-(1-2)-glycerate) occurs in both populations, but its concentration remained low and almost unchanged with increasing external osmotic pressures